Professionals in fields like dating advice work to differentiate themselves, for marketing purposes. If what you sell is rare and unique, you can sell it at a high price compared to commodity goods.
So, as expected, we see speakers, writers and coaches who heavily emphasise the uniqueness of the approach. They bring attention to the differentiating qualities of their teaching compared to that of others in the same field.
This approach stands in sharp contrast to that of the academics, and those of religious traditions. Those communities of thinkers strive to connect their work to that of their peers and antecedents. They tend to emphasise the fact that their work stands within a larger tradition.
Some level of free-thinking, maverick-like behaviour is allowed. If these qualities are somewhat stifled in traditional arenas, it’s good that they have a place to flourish in the commercial world.
But the shrewd marketing approach may lead a teacher of genuinely valuable advice to miss the opportunity to enhance his students’ understanding by exploring connected ideas from outside the packaged info he’s selling. That would be a shame.
It could also be a way of preventing confusion by keeping things focussed.
The more curious students can go explore the wider context on their own initiative, of course. Amateurs, like me, can publish our attempts to collate ideas from various sources.